title: Seven-tesla phase imaging of acute multiple sclerosis lesions: a new window into the inflammatory process.
abstract: OBJECTIVE
  In multiple sclerosis (MS), accurate, in vivo characterization of dynamic inflammatory pathological changes occurring in newly forming lesions could have major implications for understanding disease pathogenesis and mechanisms of tissue destruction. Here, we investigated the potential of ultrahigh-field magnetic resonance imaging (MRI; 7T), particularly phase imaging combined with dynamic contrast enhancement, to provide new insights in acute MS lesions.
  
  
  METHODS
  Sixteen active MS patients were studied at 7T. Noncontrast, high-resolution T2* magnitude and phase scans, T1 scans before/after gadolinium contrast injection, and dynamic contrast-enhanced (DCE) T1 scans were acquired. T2*/phase features and DCE pattern were determined for acute and chronic lesions. When possible, 1-year follow-up 7T MRI was performed.
  
  
  RESULTS
  Of 49 contrast-enhancing lesions, 44 could be analyzed. Centrifugal DCE lesions appeared isointense or hypointense on phase images, whereas centripetal DCE lesions showed thin, hypointense phase rims that clearly colocalized with the initial site of contrast enhancement. This pattern generally disappeared once enhancement resolved. Conversely, in 43 chronic lesions also selected for the presence of hypointense phase rims, the findings were stable over time, and the rims were typically thicker and darker. These considerations suggest different underlying pathological processes in the 2 lesion types.
  
  
  CONCLUSIONS
  Ultrahigh-field MRI and, especially, phase contrast, are highly sensitive to tissue changes in acute MS lesions, which differ from the patterns seen in chronic lesions. In acute lesions, the hypointense phase rim reflects the expanding inflammatory edge and may directly correspond to inflammatory byproducts and sequelae of blood-brain barrier opening.
authors.affiliation: Translational Neuroradiology Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD; Neuroimaging Research Unit, Institute of Experimental Neurology, Division of Neuroscience, San Raffaele Scientific Institute, Vita-Salute San Raffaele University, Milan, Italy.
authors.forename: Martina
authors.initials: M
authors.lastname: Absinta
authors.forename: Pascal
authors.initials: P
authors.lastname: Sati
authors.forename: María I
authors.initials: MI
authors.lastname: Gaitán
authors.forename: Pietro
authors.initials: P
authors.lastname: Maggi
authors.forename: Irene C M
authors.initials: IC
authors.lastname: Cortese
authors.forename: Massimo
authors.initials: M
authors.lastname: Filippi
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Reich
mesh_terms: D000328:Adult; D001921:Brain / Q000473:pathology*; D018450:Disease Progression; D005260:Female; D006801:Humans; D007249:Inflammation / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000473:pathology*